The field of this invention is vessel assemblies for operation at high temperatures or under other extreme conditions.
Vessels utilizing a pin-type connection to connect the vessel shell and head are known. For example, U.S. Pat. No. 3,372,828, issued to this inventor, discloses the use of both straight and tapered pins for making vessel connections. There are requirements, particularly in the nuclear industry, for a double seal between the vessel shell and head for making pressure tests while the vessel is in use. When large seal rings are used on the large vessels, the weight of the head (if the vessel is in a vertical position) may be inadequate to adequately pre-compress the seals to provide effective sealing during operation. Of course, the vessel, head, without regard to head weight, cannot pre-compress the seals when the vessel is horizontally positioned. Whenever the vessel is either horizontal or disposed in a vertical position, but is too light to effectively pre-compress the seals, some type of pre-loading device is used to pre-compress the seals.
Another problem encountered in pin-type vessels is the tendency of the radially positioned pins to move or "rachet" outwardly because of relative movement between the vessel section annular connector rings which hold the pins.